Can't get my model out of wireframe mode in blender 2.59 after saved the blender file in newer version (blender 2.79)
Maybe open the 2.59 .blend first in 2.60, then in 2.61, then in 2.62... and so on and save each time. You may skip a few if you're lucky :) (oh, in your case it might be the other way around, from 2.79 to 2.7 to 2.6... or like that, which may or may not work - but worth a try)

Here are the releases